全文获取类型
收费全文 | 2762篇 |
免费 | 352篇 |
国内免费 | 465篇 |
专业分类
测绘学 | 158篇 |
大气科学 | 620篇 |
地球物理 | 450篇 |
地质学 | 652篇 |
海洋学 | 211篇 |
天文学 | 1166篇 |
综合类 | 87篇 |
自然地理 | 235篇 |
出版年
2024年 | 14篇 |
2023年 | 31篇 |
2022年 | 44篇 |
2021年 | 51篇 |
2020年 | 65篇 |
2019年 | 66篇 |
2018年 | 45篇 |
2017年 | 68篇 |
2016年 | 46篇 |
2015年 | 102篇 |
2014年 | 140篇 |
2013年 | 170篇 |
2012年 | 117篇 |
2011年 | 157篇 |
2010年 | 128篇 |
2009年 | 219篇 |
2008年 | 203篇 |
2007年 | 226篇 |
2006年 | 224篇 |
2005年 | 218篇 |
2004年 | 182篇 |
2003年 | 156篇 |
2002年 | 135篇 |
2001年 | 112篇 |
2000年 | 113篇 |
1999年 | 120篇 |
1998年 | 120篇 |
1997年 | 57篇 |
1996年 | 54篇 |
1995年 | 45篇 |
1994年 | 39篇 |
1993年 | 29篇 |
1992年 | 11篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 5篇 |
1987年 | 10篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 5篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 2篇 |
排序方式: 共有3579条查询结果,搜索用时 15 毫秒
51.
Laboratory experiments were carried out to acquire more insight and understanding of the phenomena associated with the in-situ arsenic remediation. Visualization techniques are the most informative for the detection of Fe(II) while flowing in soils. Green Rust (GR) was considered as representative of in-situ iron precipitates. In a visualization flat cell, the change in color of GR to orange, due to oxidation, was monitored by a digital camera and the images were analyzed giving the spatial and temporal distribution of Fe(II). Moreover, both oxygen and pH changes in time were recorded in two sections along the flow direction in the cell. The measured and calculated concentration profiles were compared and the actual reaction rates were predicted. The reaction rate constants measured in this study, under flowing conditions, are in a good agreement with the values obtained from batch experiments reported in the literature. 相似文献
52.
Analyzing the tables and probability maps posted by Yan Y. Kagan and David D. Jackson in April 2002–September 2004 at http://scec.ess.ucla.edu/~ykagan/predictions_index.html and the catalog of earthquakes for the same period, the conclusion is drawn that the underlying method could be used for prediction of aftershocks, while it does not outscore random guessing when main shocks are considered. 相似文献
53.
We have found that the extensively used finite difference scheme time3d produces time fields which are 'asymmetric' in the sense that traveltimes computed to the right of the source are faster than traveltimes computed to the left. All finite difference schemes will, as they are approximations to the wave equation, to some extent fail to obey reciprocity perfectly. We show, however, that the errors in time3d may be significant—and unnecessarily large. An asymmetry in the point source initialization has been identified, and after correction time3d produces time fields with an improved reciprocity. 相似文献
54.
55.
Construction techniques for the Taklamakan Desert Highway: research on the construction materials and the results of field tests 总被引:1,自引:0,他引:1
After conducting many laboratory and field experiments, several key technical issues related to the construction of China’s
Taklamakan Desert Highway have been satisfactorily resolved. In particular, considerable progress has been made on the dry
compaction of a sand sub-base, road design parameters, the creation of a structure that combines a sub-grade and asphalt pavement,
analysis of the stability of a sand sub-base strengthened with geotextiles, and on the development of a complete set of construction
techniques. The achievements of this research were successfully applied for the first time in the Taklamakan Desert, where
the environmental conditions are extremely harsh. The results suggest that the construction of this highway was economical
and that the simple construction methods produced a reliable highway. The resulting highway is believed to be the world’s
first long-distance graded highway running through a huge desert with migrating dunes. 相似文献
56.
长江中下游夏季高温灾害机理及预测 总被引:16,自引:1,他引:16
利用我国1961-2003年夏季(6—8月)高温资料,建立长江中下游地区主要城市强高温及高温过程较完整的时间序列,探讨了该地区主要城市高温气候特征。分析该地区南京、杭州、南昌等城市夏季高温灾害机理,东亚副热带高压是造成长江中下游地区城市夏季高温的主要影响系统。在此基础上用均生函数-最佳子回归集构造预测模型,预测夏季月高温出现日数,通过42a高温资料预报检验,有较好的预测效果,值得在业务中应用。 相似文献
57.
针对参数回归技术制作概率预报存在拟合好、但预报结果不稳定的现象, 提出了用K近邻非参数回归技术制作概率预报的新途径。K 近邻非参数回归技术包括历史样本数据库、近邻子集生成和优化以及预报量估计4 个主要部分。利用该技术进行了单要素概率预报(主要包括云量和降水)和多维联合概率预报(降水、总云量、风速和气温)试验, 并对试验结果进行了检验。实例研究结果表明:该文所给出的计算方案预报稳定性好, 准确率较高,具有良好的业务应用价值。 相似文献
58.
59.
60.